APPLICATION
Probably no other type of conveyor is applied to so many gravity
materials handling uses as roller and wheel conveyor, handling
various packaged materials efficiently for distances as short as 2
ft. or as long as 100 ft. or more. Any item from light bulbs to
bagged cement to heavy castings can be moved on gravity.
Most items are best handled on roller conveyor, however, wheel
conveyor may be substituted where a portable type gravity conveyor
is required, where light weight containers (38 lbs. per ft. in
steel, 18 lbs. per ft. in aluminum) are to be handled and where
semi-rigid filled multi-wall paper bags or bales are to be
handled. In general, roller conveyor should not be used for
conveying burlap bags of coffee beans, paper or cotton bags of
rice, cotton bags of flour or freshly filled paper bags of cement
because the type of material mentioned has a tendency to drape
over rollers.
Conveyors, when properly applied, confine the flow of materials
thus conserving valuable production and storage space. Frequently,
as in storage racks and production assembly lines, roller or wheel
conveyor are used for storage providing accessibility and easy
movement for processing or production. Breakage or damage is
generally minimized when the products are supported and restricted
during the travel on conveyor.
Supports should have some height adjustment and should be selected
for convenient height for personnel.
CONVEYOR SELECTION
Skatewheel conveyor, as a rule, is generally used for handling
smooth bottom, wood, fiber or plastic containers. Semi-rigid
smooth bottom bags or bales may also be conveyed on some wheel
conveyor. If there is any doubt, the product and container should
be tested on an appropriate wheel conveyor. Such testing can help
determine the suitable grade.
Skatewheel conveyor is not recommended for handling cans with
chimes, open bottom crates, cleated containers or damp, soft,
soggy cartons. It is further not recommended for conveying
flexible filled bags or articles too small to span at least three
rows of wheels. Extremely heavy or soft-bottomed cartons may fold
around wheels and are therefore also not recommended for use on
wheel conveyor.
From the Hytrol Catalog, you will note that skatewheel conveyor is
available in varied widths and varied wheels per foot patterns.
The selection of wheel conveyor is based upon the rigidity, size
and weight of package to be conveyed. The denser the wheel
pattern, the greater the range of cartons that can be handled on
such wheel conveyor.
Roller conveyor are also used for handling smooth bottom, wood,
fiber or plastic containers, crates (without wire binding), drums
and cans with chimes, kegs and long narrow packaged materials.
Gravity conveyors are used as a level push line or down grade by
utilizing the natural force of gravity. The use of gravity to
convey the selected class of packages to move by their own weight,
on a bed of rollers or wheels, is, perhaps, the most widely used
means for conveying in industry. The weights to be conveyed may
vary from a few ounces to several tons. For example, in department
stores, conveyors are used for handling light weight boxes of
hosiery and the same conveyors handle heavier boxes of dishes and
appliances. The selection of rollers is tailored to fit the
application.
Roller conveyor is not recommended for conveying soft bottom
cartons or bags which will flex and fold or wrap around the upper
carrying portion of the roller and thus deter the free motion of
such containers.
The degree of decline required will vary depending on whether the
bearings are dry or grease packed, on the ambient temperature (if
outdoors) and, in some areas, on humidity. The degree of decline
also depends on the specific application. The first package will
start rotation of the rollers. The second package if it followed
shortly, would benefit from this rotation and would travel a bit
faster than the first package and the third package even faster.
In the course of the day's production, trains of packages could be
traveling very fast on a degree of decline originally defined to
start package movement from rest. Retarding devices to help
control this situation are available.
A few elementary rules in the selection of roller conveyor are
offered as follows:
(1.) Packages to be handled should, in general, have smooth firm
bottom riding surface.
(2.) For normal conveying, at least three (3) rollers should be
under the package being conveyed at all times.
(3.) To select the proper roller, divide the weight of the package
by the number of rollers supporting the package. The load capacity
charts in the Hytrol General Catalog will help in your selection.
Other important areas to be considered are the actual items to be
conveyed as well as their size. While the load capacity chart
indicates that 50 lb. empty oil drums could be conveyed on
1.9" Dia. x 16 Ga. rollers, we would recommend the use of
2" Dia. x 12 Ga. rollers because of the greater wall
thickness in handling a steel drum.
The tolerances of the various components, which make up a roller
conveyor, may be such as to not present a perfect conveying
surface. Uniformly loaded packages, with some flexibility, will
distribute the weight approximately to each roller supporting the
package, whereas rigid packages may impose their entire load on a
reduced number of rollers. Wood or steel pallets may actually be
supported by only 50 per cent of the rollers under them. Select
from the Hytrol General Catalog a roller to suit the required load
capacity, taking into consideration the type of product being
handled, so that in the event the load is actually supported by
one-half of the rollers under the product. The rollers selected
will actually support this type of load. When roller lengths
exceed the catalog lengths, the axle deflection may be the
limiting factor in place of ball bearing capacity. Package roller
conveyors are not normally considered to be precision equipment,
and past experience indicates that the tops of all of the rollers
in the conveyor may not be at exactly the same height. Where an
excessive impact might occur in the loading area of a conveyor, it
is advisable to consider providing twice the number of rollers
normally required for conveying the package in this loading area
only.
Nominal roller length is determined by the maximum width of the
commodity to be conveyed. Ordinarily, rollers would be two to
three inches longer than the widest package within the standards
listed in the Hytrol General Catalog. It is, however, permissible,
in certain package handling situations, for the package to extend
beyond the ends of the rollers if the rollers are mounted in a
high position in the side frames and provided the bottom of the
package does not flex and make contact with the side frames.
Grades
While it is difficult to recommend specific grades for various
materials to be conveyed on wheel or roller conveyer, we offer the
following suggested grades based upon average conditions. The
actual grade for a specific requirement should be determined by
test. Grades required for roller conveyer may vary because light
cartons with soft bottoms may require more grade than heavy
packages with hard bottoms.
Grades on curves are based upon the length of the outside rail and
grades on straight roller curves should be increased 25 to 50
percent than charted in fig. 7.
The average roller conveyor line handling 40 to 45 lb. packages
and equipment with ball bearing rollers requires a pitch of about
½" per lineal foot of travel, and for wheel conveyor the
pitch is about 3/8" per lineal foot of travel. The pitch will
increase or decrease according to the riding surface and the
weight of the commodity to be conveyed. Also, the use of sleeve
(sanitary) type bearings will affect the conveyor pitch.
CURVES
Roller and wheel conveyor curves are made to match the straight
conveyor. The radii of any curve are dependent upon the length and
width of the package to be conveyed. The length and width of the
package also determines the width (between rails) of the curve and
generally, the width of the curve determines the width of the
adjacent connecting straight conveyor. If a package is
exceptionally long, as for florescent light tubes or cut flowers,
the adjacent straight conveyor might normally be excessively wide
for such a package, which condition, of course creates a costly
conveyor. The imbalance of this type of situation can be corrected
by using a narrower width curve and offset guard rails thus
permitting the package to overhang the rollers on the curve but
still keep the adjacent straight conveyor to a satisfactory width
and help keep the price of the required conveyor within
competitive limitations.
Wheel curves, because of the multiple rows of individual ball
bearing wheels, perform an excellent job of conveying rectangular
packages, as the individual wheels apply the necessary
differential action to keep the package centered as it traverses
the curve. Hytrol wheel curves are available in standard overall
widths to join to adjacent straight sections, with 45° and 90°
of curvature as standard.
Hytrol also has available tapered steel rollers, which also apply
the necessary differential action to keep the package centered as
it travels through the curve.
Straight roller curves are generally more satisfactory for
handling cylindrical packages rather than rectangular packages
because of the lack of the differential action required on this
type of roller conveyer. Since a package has a longer distance to
travel adjacent to the outer rail, the package in this type of
curve has a tendency to slip to the outer frame.
Double roller (curves with a center frame midway between the two
outer frames which splits the roller length) will convey a square
or rectangular package better than the single straight roller
curve because of the differential action of the two separate lanes
of rollers.
For best results, gravity curves should have a straight gravity
roller conveyor section at the infeed and the discharge ends of
the curve of minimum length equal to approximately 2/3 of the
length of the package.
Gravity curves are not recommended for accumulation of square or
rectangular packages. The line pressure will prevent the packages
from maneuvering the gravity curves and generally will force the
package against the outer guard thus blocking the free flow of
further packages.
SPURS
Gravity roller or wheel conveyor spurs are used for merging and
diverging of packages onto or off of a main line transportation
conveyor. The standard angles are 30°, 45° and 90°. The 45°
diverging unit is not normally recommended for automatic diverging
of packages but should be manually attended. Turning wheels should
be used as shown in the Hytrol General Catalog where spurs are
used in the converging application.
"Y" AND SPUR CURVE SWITCHES
These switches utilizing skate wheels provide a simple method of
diverting or converging products from one line to another as
described in the Hytrol General Catalog.
GATE SECTIONS
These are hinged sections used as gates and are available for
vertical movement of the section to provide access for personnel,
lift trucks or other equipment. They are available with or without
springs. The springs provide some assistance in lifting the
heavier gate sections. Horizontal gate sections with a pivot pin
on one end and caster supports on the opposite end are also
available.
ROLLER CONSTRUCTION
Thin wall rollers are perfectly satisfactory for most package
handling, but should not be used for handling extremely heavy
packages with steel strapping or filled steel drums regardless of
the indicated roller capacity. Thin wall rollers may be easily
bent, dented or cut, thus impairing their usefulness. The heavier
rollers such as 2 ½" Dia. x 11 Ga., 2 9/16" Dia. x 7
Ga., and 3 ½" Dia. x 9 Ga. are much better suited for this
latter application.
AXLES
Spring-Loaded axle construction is a Hytrol standard for:
1 3/8" Dia. x 18 Ga. Rollers using ¼" Dia. Galv. steel
axles 1.9" Dia. x 16 Ga. Rollers using 7/16" Hex. steel
axles 2" Dia. x 12 Ga. Rollers using 7/16" Hex. steel
axles 2 ½" Dia. x 11 Ga. Rollers using 11/16" Hex.
steel axles 2 9/16" Dia. x 7 Ga. Rollers using 11/16"
Hex. steel axles.
The spring-loaded construction which requires no hog rings or
cotter pins permits the customer to easily remove and relocate or
replace rollers.
COUPLINGS
Other than wheel conveyor and 1 3/8" Dia. roller conveyor,
which have bar and hook type couplings, all other frames have butt
couplings for bolting sections together.
SUPPORTS
Hytrol stationary supports are available in light, medium and
heavy duty styles. Consult the Hytrol General Catalog for further
information.
Poly-tier supports for support of multi-level conveyor lines are
also described in the Hytrol General Catalog.
Ceiling hangers are 5/8" Dia. painted steel rods with
threaded ends.
Tripod stands are useful in setting up temporary conveyor lines,
using skatewheel and/or 1 3/8" Dia. x 18 Ga. roller conveyor.
For other types of supports, consult the Hytrol General Catalog.
GUARD RAILS
Most overhead conveyor are usually required to be provided with
guardrails both sides. Curves as an option, may also be provided
with guards at the outside rail. Consult the Hytrol General
Catalog for various types.
FRAMES
Some frames are of steel galvanized, heat-treated aluminum, and
powdercoat painted steel. Hytrol green is our standard color.
REPLACEMENT ROLLERS
You will at times, receive request to quote on replacement rollers
even for frames, which may have been furnished by other than
Hytrol. It is extremely important that exact information be
furnished. DO NOT GUESS.
1. Obtain roller diameter and gauge.
2. Check axle size; i.e. ¼" Dia., 7/16" Hex,
11/16" Hex. etc. on 1 3/8" Dia. x 18 Ga. rollers, Hytrol
furnishes ¼" Dia. Galv. steel spring loaded axles. Other
conveyor suppliers may use 5/16" hex axles.
3. Check to see if bearings are dry, grease packed or re-greasable.
4. Measure the exact distance between existing frames.
5. Measure the frame thickness, i.e. 12 Ga., 10 Ga., 3/16",
¼" etc.
6. Some customers re-use their existing axles. Determine if axles
should be furnished. If the customer uses rollers with
spring-loaded axles, it is best that we furnish these complete.
QUESTIONS:
If you have questions, the answers to which are not to be found in
Hytrol Catalogs, do not hesitate to call your master Hytrol
Distributor. He will obtain the information for you. Do not place
collect calls to your master distributor.
